1. Field of the Invention
The present invention relates to axle assemblies for motor vehicles in general, and more particularly to a rigid drive axle assembly including a support beam member having a substantially flat central section and two opposite axle shaft members rotatably supported in a spaced relationship with respect to the central section of the support beam member.
2. Description of the Prior Art
Rigid drive axle assemblies are well known structures that are in common use in most motor vehicles. Such axle assemblies include a number of components that are adapted to transmit rotational power from an engine of the motor vehicle to wheels thereof. Typically, the rigid drive axle assembly includes a hollow axle housing, a differential, which is rotatably supported within the axle housing by a non-rotating carrier. The differential is connected between an input drive shaft extending from the vehicle engine and a pair of output axle shafts extending to the vehicle wheels. The axle shafts are contained in respective non-rotating tubes that are secured to the carrier. Thus, rotation of the differential by the drive shaft causes corresponding rotation of the axle shafts. The carrier and the tubes form a housing for these drive train components of the axle assembly, inasmuch as the differential and the axle shafts are supported for rotation therein.
The axle housings are generally classified into two basic types. The first axle housing type is a unitized carrier construction, commonly referred to as a Salisbury or Spicer type axle assembly, illustrated in FIG. 1. In this structure, the Salisbury type axle assembly 301 includes a carrier 312 (which houses the rotatable differential mechanism 340) is directly connected to the two tubes 316 and 317 (which house the rotatable axle shafts 320). An opening is provided at the rear of the carrier to permit assembly of the differential therein. A cover 326 closes this opening during the use. The cover 326 is connected by bolts 328 to a rear face 330 of the carrier 312 hydraulically seals the housing against the passage of lubricant. A brake assembly 314 located at the end of a tube 316 extending outboard from the ends of an axle carrier 312. Located within the differential case is a drive pinion 332 rotatably supported by a rear drive pinion bearing 334 and a front drive pinion bearing (not shown) supported on the inner surface of a portion of the axle carrier casing 338 that extends forward from the center line of the axle assembly. A driveshaft, driveably connected to the output shaft of a transmission, is coupled to the shaft of the drive pinion 332. The differential mechanism 340, located within the differential case 348, includes a ring gear 342, in continuous meshing engagement with drive pinion 332 and supported rotatably on the differential rear drive pinion bearing 334 and the front drive pinion bearing located within the housing gear and cylindrical extension 338 of the carrier 312. The axle carrier 312 also includes laterally directed tubular extensions 344, 346, which receive therein the ends of housing tubes 316 and 317, respectively. Located within the carrier 312 is a differential case 348, on which bevel pinion gears 350, 352 are supported for rotation on a differential pinion shaft 354. Side bevel gears 356, 358 are in continuous meshing engagement with pinions 350, 352 and are driveably connected to left and right axle shafts 320, located respectively within tubes 316 and 317. The axle shaft 320 is connected to the corresponding side bevel gear 356. Unitized carrier axle housing constructions of this type are economical to manufacture and are readily adaptable for a variety of vehicles.
The second axle housing type is a separable carrier construction, and is commonly referred to as a Banjo type axle, illustrated in FIG. 2. In this structure, the Banjo type axle 401 includes an axle housing 402 having axle tubes 406a and 406b connected together by a central member 404. The axle tubes 406a and 406b are adapted to receive and rotatably support output axle shafts 414a and 414b. The axle housing 402 is formed separate and apart from a carrier 422. This central member 404 is generally hollow and cylindrical in shape, having a large generally circular opening 410 formed therethrough. During assembly, a differential 420 is first assembled within the carrier 422, then the carrier 422 is secured to the central member 404 of the axle housing 402. The overall shape of this type of axle housing (i.e., the generally round shape of the central member 404 and the elongated tubes 406a and 406b extending therefrom) generally resembles the shape of a banjo musical instrument. Hence, this type of axle housing is referred to as the Banjo type axle housing. The Banjo type axle housings are advantageous because the carrier 422 and differential 420 can be removed from the axle assembly 401 for service without disturbing the other components thereof.
However, both Banjo and Salisbury type axles have their disadvantages. Thus, there is a need for a rigid drive axle assembly that combines the advantages of both Banjo and Salisbury type axles and lessens their shortcomings.
The present invention provides a novel rigid drive axle assembly for motor vehicles. The rigid drive axle assembly in accordance with the present invention comprises a support beam member having a substantially flat, enlarged central section and two opposite arm sections axially outwardly extending from the central section. The drive axle assembly further comprises a differential assembly fastened to the enlarged central section of the support beam member, and two opposite axle shaft members outwardly extending from the differential assembly, and rotatably supported by the arm sections of the support beam member so that the axle shaft members are spaced from the central section of the support beam member in a driving direction of the motor vehicle. Distal ends of the axle shaft members are provided with flange members adapted for mounting corresponding wheel hubs.
The differential assembly includes a differential carrier frame member fastened to the central section of the support beam member, and provided for rotatably supporting a differential case and a drive pinion. The differential case houses a conventional differential gear mechanism, well known to those skilled in the art. The drive pinion has a pinion gear in continuous meshing engagement with a ring gear, and a pinion shaft operatively coupled to a vehicular drive shaft driven by a vehicular powerplant through an input yoke. The differential assembly is enclosed into a housing formed by a rear cover and a front cover secured to opposite surfaces of the central section of the beam member in any appropriate manner well known in the art. The front cover has a font opening for rotatably supporting and receiving therethrough a distal end of the pinion shaft of the drive pinion. The rear cover incorporates two opposite through holes for receiving the axle shaft members therethrough. Each of the through holes is provided with a self-centering seal.
The differential carrier frame member is, preferably, a single-piece metal part manufactured by casting or forging. The differential carrier frame member has a generally Y-shaped configuration and includes a neck portion and two opposite, axially spaced, coaxial bearing hub portions attached to the neck portion through respective leg portions. The neck portion has an opening therethrough adapted for receiving and rotatably supporting the drive pinion through an appropriate anti-friction bearing, preferably a roller bearing. The bearing hub portions are provided with respective openings therethrough adapted for receiving appropriate anti-friction bearings for rotatably supporting the differential carrier. Moreover, the bearing hub portions are provided with mounting flange portions.
In accordance with the first exemplary embodiment of the present invention, the support beam member has the substantially flat, enlarged central section and the two opposite, substantially rectangular arm sections axially outwardly extending from the central section. Preferably, the support beam member is formed of a single-piece C-channel body manufactured by a metal deforming, such as stamping, having a substantially flat, enlarged central section and two opposite arm sections axially outwardly extending from the central section. The flat enlarged central section is further provided with a central opening therethrough adapted for receiving the differential carrier frame member of the differential assembly. The support beam member further includes two structural plates attached to the arm sections so as to form the tubular arm sections of substantially rectangular cross-section.
In accordance with the second exemplary embodiment of the present invention, the support beam member has the substantially flat, enlarged central section and the two opposite, substantially cylindrical arm sections axially outwardly extending from the central section. Preferably, the support beam member is formed of a single-piece C-channel body manufactured by a metal deforming, such as stamping, having a substantially flat, enlarged central section and two opposite arm sections axially outwardly extending from the central section. The flat enlarged central section is further provided with a central opening therethrough adapted for receiving the differential carrier frame member of the differential assembly. The arm sections of the single-piece C-channel body are deformed so as to form the substantially cylindrical arm sections of the support beam member.
In accordance with the third exemplary embodiment of the present invention, the support beam member has a substantially flat, enlarged central section and two opposite substantially flat arm sections axially outwardly extending from the central section. Preferably, in this embodiment, the support beam member is formed of a substantially flat integral profiled body. Preferably, the body is a substantially flat, I-shaped metal profile.
The body has an enlarged central section and two opposite arm sections axially outwardly extending from the central section. The enlarged central section of the body defines the central section of the support beam member. The enlarged central section is further provided with a central opening therethrough adapted for receiving the differential carrier frame member. Fixed at distal ends of the arm sections of the support beam member are corresponding shaft supporting brackets. Each of the shaft supporting brackets has a hole therethrough adapted to receive and rotatably support the axle shaft members in a spaced relationship with respect to the body of the support beam member.
Therefore, the axle assembly in accordance with the present invention represents a novel arrangement of the drive axle assembly providing a number of advantages over the currently employed Salisbury and Banjo style axles, such as improved strength to weight ratio, ease of manufacturing and reduced manufacturing cost due to the use of simple metal stampings to produce the support beam member and the front cover, ease of assembly/disassembly and servicing of the axle assembly, and improved modularity and commonality of axle components.